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Sep 19, 2013
09/13

by
Leonardo Modesto

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In this paper we study the gravitational collapse in loop quantum gravity. We consider the space-time region inside the Schwarzschild black hole event horizon and we divide this region in two parts, the first one where the matter (dust matter) is localized and the other (outside) where the metric is Kantowski-Sachs type. We calculate the state solving Hamiltonian constraint and we obtain a set of three difference equations that give a regular and natural evolution beyond the classical...

Source: http://arxiv.org/abs/gr-qc/0610074v1

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Sep 21, 2013
09/13

by
Leonardo Modesto

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In this paper we calculated the spectral dimension of loop quantum gravity (LQG) using the scaling property of the area operator spectrum on spin-network states and using the scaling property of the volume and length operators on Gaussian states. We obtained that the spectral dimension of the spatial section runs from 1.5 to 3, and under particular assumptions from 2 to 3 across a 1.5 phase when the energy of a probe scalar field decreases from high to low energy in a fictitious time T. We...

Source: http://arxiv.org/abs/0905.1665v1

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Sep 18, 2013
09/13

by
Leonardo Modesto

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In this paper we calculate modifications to the Schwarzschild solution by using a semiclassical analysis of loop quantum black hole. We obtain a metric inside the event horizon that coincides with the Schwarzschild solution near the horizon but that is substantially different at the Planck scale. In particular we obtain a bounce of the two-sphere for a minimum value of the radius and that it is possible to have another event horizon close to the r=0 point.

Source: http://arxiv.org/abs/gr-qc/0611043v2

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Sep 23, 2013
09/13

by
Leonardo Modesto

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In this paper we work in perturbative quantum gravity and we introduce a new effective model for gravity. Expanding the Einstein-Hilbert Lagrangian in graviton field powers we have an infinite number of terms. In this paper we study the possibility of an interpretation of more than three graviton interacting vertices as effective vertices of a most fundamental theory that contain tensor fields. Here we introduce a Lagrangian model named I.T.B (Intermediate Tensor Boson) where four gravitational...

Source: http://arxiv.org/abs/hep-th/0312318v2

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Sep 23, 2013
09/13

by
Leonardo Modesto

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In this paper we introduce a perturbatively super-renormalizable and unitary theory of quantum gravity in any dimension D. The theory presents two entire functions, a.k.a. "form factors", and a finite number of local operators required by the quantum consistency of the theory itself. The main reason to introduce the entire functions is to avoid ghosts (states of negative norm) like the one in the four-dimensional Stelle's theory. The new theory is indeed ghost-free since the two...

Source: http://arxiv.org/abs/1202.3151v1

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Jun 29, 2018
06/18

by
Leonardo Modesto

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We propose a class of multidimensional higher derivative theories of gravity without extra real degrees of freedom besides the graviton field. The propagator shows up the usual real graviton pole and extra complex conjugates poles that do not contribute to the absorptive part of the physical scattering amplitudes. Indeed, they may consistently be excluded from the asymptotic observable states of the theory making use of the Lee-Wick and Cutkoski, Landshoff, Olive and Polkinghorne prescription...

Topics: High Energy Physics - Theory, High Energy Physics - Phenomenology, General Relativity and Quantum...

Source: http://arxiv.org/abs/1602.02421

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Sep 20, 2013
09/13

by
Leonardo Modesto

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In this paper we obtain the black hole metric from a semiclassical analysis of loop quantum black hole. Our solution and the Schwarzschild one tend to match well at large distances from Planck region. In r=0 the semiclassical metric is regular and singularity free in contrast to the classical one. By using the new metric we calculate the Hawking temperature and the entropy. For the entropy we obtain the logarithmic correction to the classical area law. Finally we study the mass evaporation...

Source: http://arxiv.org/abs/gr-qc/0612084v1

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Sep 22, 2013
09/13

by
Leonardo Modesto

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We review a class of higher derivative theories of gravity consistent at quantum level. This class is marked by a non-polynomal entire function (form factor), which averts extra degrees of freedom (including ghosts) and improves the high energy behaviour of the loop amplitudes. By power counting arguments, it is proved that the theory is super-renormalizable, i.e. only one-loop divergences survive. At classical level, black holes and cosmological solutions are singularity free.

Source: http://arxiv.org/abs/1302.6348v1

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Jul 20, 2013
07/13

by
Leonardo Modesto

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In this paper we study perturbatively an extension of the Stelle higher derivative gravity involving an infinite number of derivative terms. We know that the usual quadratic action is renormalizable but suffers of the unitarity problem because of the presence of a ghost (state of negative norm) in the theory. The new theory is instead ghost-free since the introduction of (in general) two entire functions in the model with the property do not introduce new poles in the propagator. The local high...

Source: http://arxiv.org/abs/1107.2403v1

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Sep 23, 2013
09/13

by
Leonardo Modesto

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We extend the ideas introduced in the previous work to a more general space-time. In particular we consider the Kantowski-Sachs space time with space section with topology $R \times S^2$. In this way we want to study a general space time that we think to be the space time inside the horizon of a black hole. In this case the phase space is four dimensional and we simply apply the quantization procedure suggested by Loop Quantum Gravity and based on an alternative to the Schroedinger...

Source: http://arxiv.org/abs/gr-qc/0411032v2

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Sep 18, 2013
09/13

by
Leonardo Modesto

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In this paper we consider the Kantowski-Sachs space-time in Ashtekar variables and the quantization of this space-time starting from the complete loop quantum gravity theory. The Kanthowski-Sachs space-time coincides with the Schwarzschild black hole solution inside the horizon. By studying this model we can obtain information about the black hole singularity and about the dynamics across the point r=0. We studied this space-time in ADM variables in two previous papers where we showed that the...

Source: http://arxiv.org/abs/gr-qc/0509078v2

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Sep 22, 2013
09/13

by
Leonardo Modesto

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In this paper we have improved the semiclassical analysis of loop quantum black hole (LQBH) in the conservative approach of constant polymeric parameter. In particular we have focused our attention on the space-time structure. We have introduced a very simple modification of the spherically symmetric Hamiltonian constraint in its holonomic version. The new quantum constraint reduces to the classical constraint when the polymeric parameter goes to zero.Using this modification we have obtained a...

Source: http://arxiv.org/abs/0811.2196v1

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Sep 18, 2013
09/13

by
Leonardo Modesto

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In this paper we work in perturbative Quantum Gravity coupled to Scalar Matter at tree level and we introduce a new effective model in analogy with the Fermi theory of weak interaction and in relation with a previous work where we have studied only the gravity and its self-interaction. This is an extension of the I.T.B model (Intermediate-Tensor-Boson) for gravity also to gravitational interacting scalar matter. We show that in a particular gauge the infinite series of interactions containing...

Source: http://arxiv.org/abs/hep-th/0401013v1

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Jun 30, 2018
06/18

by
Leonardo Modesto

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We advance a class of unitary higher derivative theories of gravity that realize an ultraviolet completion of Einstein general relativity in any dimension. This range of theories is marked by an entire function, which averts extra degrees of freedom (including poltergeists) and improves the high energy behavior of the loop amplitudes. It is proved that only one-loop divergences survive and the theory can be made super-renormalizable regardless of the spacetime dimension. Moreover, using the...

Topics: High Energy Physics - Theory, High Energy Physics - Phenomenology, General Relativity and Quantum...

Source: http://arxiv.org/abs/1402.6795

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Sep 21, 2013
09/13

by
Leonardo Modesto

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We apply techniques recently introduced in quantum cosmology to the Schwarzschild metric inside the horizon and near the black hole singularity at r = 0. In particular, we use the quantization introduced by Husain and Winkler, which is suggested by Loop Quantum Gravity and is based on an alternative to the Schrodinger representation introduced by Halvorson. Using this quantization procedure, we show that the black hole singularity disappears and spacetime can be dynamically extended beyond the...

Source: http://arxiv.org/abs/gr-qc/0407097v2

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Sep 18, 2013
09/13

by
Leonardo Modesto

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We apply the recent results in Loop Quantum Cosmology and in the resolution of Black Hole singularity to the gravitational collapse of a star. We study the dynamic of the space time in the interior of the Schwarzschild radius. In particular in our simple model we obtain the evolution of the matter inside the star and of the gravity outside the region where the matter is present. The boundary condition identify an unique time inside and outside the region where the matter is present. We consider...

Source: http://arxiv.org/abs/gr-qc/0504043v1

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Sep 19, 2013
09/13

by
Leonardo Modesto

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In this paper we summarize "loop quantum gravity" (LQG) and we show how ideas developed in LQG can solve the black hole singularity problem when applied to a minisuperspace model.

Source: http://arxiv.org/abs/hep-th/0701239v1

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Sep 22, 2013
09/13

by
Leonardo Modesto

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In this paper we have calculated the spectral dimension of loop quantum gravity (LQG) using simple arguments coming from the area spectrum at different length scales. We have obtained that the spectral dimension of the spatial section runs from 2 to 3, across a 1.5 phase, when the energy of a probe scalar field decrees from high to low energy. We have calculated the spectral dimension of the space-time also using results from spin-foam models, obtaining a 2-dimensional effective manifold at...

Source: http://arxiv.org/abs/0812.2214v1

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Jun 30, 2018
06/18

by
Gianluca Calcagni; Leonardo Modesto

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We construct a ultraviolet completion of the bosonic sector of 11-dimensional supergravity motivated by string field theory. We start from a general class of theories characterized by an entire nonpolynomial form factor which allows one to avoid new poles in the propagator and improves the high-energy behavior of the loops amplitudes. Comparing these models with effective string field theory, a unique form factor is selected out. In view of this, we modify 10-dimensional supergravity and...

Topics: High Energy Physics - Theory, Mathematics, Mathematical Physics

Source: http://arxiv.org/abs/1404.2137

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Sep 22, 2013
09/13

by
Pietro Fre'; Leonardo Modesto

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In the previous submission of this paper we claimed to have solved the problem of constructing a consistent non-abelian Born Infeld action which is $\kappa$--supersymmetric to all orders. Our method was based on an extension of target superspace to $\mathrm{N} \times \mathrm{N}$ matrix--valued objects for all the items appearing in the geometric construction. Then we applied the \textit{double first order formalism} introduced by us in the previous construction of abelian brane actions to the...

Source: http://arxiv.org/abs/hep-th/0310217v2

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Jul 20, 2013
07/13

by
Cosimo Bambi; Leonardo Modesto

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In 4-dimensional General Relativity, there are several theorems restricting the topology of the event horizon of a black hole. In the stationary case, black holes must have a spherical horizon, while a toroidal spatial topology is allowed only for a short time. In this paper, we consider spinning black holes inspired by Loop Quantum Gravity and by alternative theories of gravity. We show that the spatial topology of the event horizon of these objects changes when the spin parameter exceeds a...

Source: http://arxiv.org/abs/1107.4337v2

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Sep 21, 2013
09/13

by
Eugenio Bianchi; Leonardo Modesto

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The relation between Loop Quantum Gravity and Regge calculus has been pointed out many times in the literature. In particular the large spin asymptotics of the Barrett-Crane vertex amplitude is known to be related to the Regge action. In this paper we study a semiclassical regime of Loop Quantum Gravity and show that it admits an effective description in terms of perturbative area-Regge-calculus. The regime of interest is identified by a class of states given by superpositions of four-valent...

Source: http://arxiv.org/abs/0709.2051v2

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Sep 19, 2013
09/13

by
Pietro Fré; Leonardo Modesto

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We introduce a new first order formulation of world-volume actions for p-branes with k-supersymmetry. In this language, which involves more auxiliary fields compensated by more local symmetries, the action is provided by a very compact, simple and elegant formula applicable to any supergravity background. The k-supersymmetry variation against which it is invariant is obtained from the bulk supersymmetries by means of a projector that has a simple expression in terms of the auxiliary fields. The...

Source: http://arxiv.org/abs/hep-th/0206144v3

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Jun 29, 2018
06/18

by
Stefano Giaccari; Leonardo Modesto

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We derive the N=1 supersymmetric extension for a class of weakly nonlocal four dimensional gravitational theories.The construction is explicitly done in the superspace and the tree-level perturbative unitarity is explicitly proved both in the superfield formalism and in field components. For the minimal nonlocal supergravity the spectrum is the same as in the local theory and in particular it is ghost-free. The supersymmetric extension of the super-renormalizable Starobinsky theory and of two...

Topics: High Energy Physics - Theory, High Energy Physics - Phenomenology, General Relativity and Quantum...

Source: http://arxiv.org/abs/1605.03906

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0.0

Jun 29, 2018
06/18

by
Leonardo Modesto; Leslaw Rachwal

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We explicitly prove that a class of finite quantum gravitational theories (in odd as well as in even dimension) is actually a range of anomaly-free conformally invariant theories in the spontaneously broken phase of the conformal Weyl symmetry. At classical level we show how the Weyl conformal invariance is likely able to tame the spacetime singularities that plague not only Einstein gravity, but also local and weakly non-local higher derivative theories. This latter statement is rigorously...

Topics: High Energy Physics - Theory, Cosmology and Nongalactic Astrophysics, Mathematics, Astrophysics,...

Source: http://arxiv.org/abs/1605.04173

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Sep 22, 2013
09/13

by
Emanuele Alesci; Leonardo Modesto

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We study the black hole particle production in a regular spacetime metric obtained in a minisuperspace approach to loop quantum gravity. In different previous papers the static solution was obtained and shown to be singularity-free and self-dual. In this paper expanding a previous study of the black hole dynamics we repeat the Hawking analysis which leads to a thermal flux of particles at the future infinity. The evaporation time is infinite and the unitarity is recovered due to the regularity...

Source: http://arxiv.org/abs/1101.5792v1

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Sep 17, 2013
09/13

by
Leonardo Modesto; Andrew Randono

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It has been known for some time that there is a deep connection between thermodynamics and gravity, with perhaps the most dramatic implication that the Einstein equations can be viewed as a thermodynamic equation of state. Recently Verlinde has proposed a model for gravity with a simple statistical mechanical interpretation that is applicable in the non-relatvistic regime. After critically analyzing the construction, we present a strong consistency check of the model. Specifically, we consider...

Source: http://arxiv.org/abs/1003.1998v1

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Jun 30, 2018
06/18

by
Leonardo Modesto; Leslaw Rachwal

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We hereby introduce and extensively study a class of non-polynomial higher derivative theories of gravity that realize a ultraviolet (UV) completion of Einstein general relativity. These theories are unitary (ghost free) and at most only one-loop divergences survive. The outcome is a class of theories super-renormalizable in even dimension and finite in odd dimension. Moreover, we explicitly prove in D=4 that there exists an extension of the theory that is completely finite and all the beta...

Topics: High Energy Physics - Theory, Mathematics, Mathematical Physics, General Relativity and Quantum...

Source: http://arxiv.org/abs/1407.8036

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Sep 21, 2013
09/13

by
Francesco Caravelli; Leonardo Modesto

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In this paper we perform the calculation of the spectral dimension of the space-time in 3d quantum gravity using the dynamics of the Ponzano-Regge vertex (PR) and its quantum group generalization (Turaev-Viro model (TV)). We realize this considering a very simple decomposition of the 3d space-time and introducing a boundary state which selects a classical geometry on the boundary. We obtain that the spectral dimension of the space-time runs from 2 to 3, across a 1.5 phase, when the energy of a...

Source: http://arxiv.org/abs/0905.2170v1

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Sep 18, 2013
09/13

by
Pietro Frè; Leonardo Modesto

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The new first order, rheonomic, kappa-supersymmetric formalism recently introduced by us for the world-volume action of the D3-brane is extended to the case of D5-branes. This extension requires the dual formulation of the Free Differential Algebra of type IIB supergravity in terms of 6-form gauge potentials which was so far missing and is given here. Furthermore relying on our new approach we are able to write the D5-world volume action in a manifestly SL(2,R) covariant form. This is important...

Source: http://arxiv.org/abs/hep-th/0212287v2

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Jun 27, 2018
06/18

by
Leonardo Modesto; Leslaw Rachwal

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It is well known that standard gauge theories are renormalizable in D=4 while Einstein gravity is renormalizable in D=2. This is where the research in the field of two derivatives theories is currently standing. We hereby present a class of weakly non-local higher derivative gravitational and gauge theories universally consistent at quantum level in any spacetime dimension. These theories are unitary (ghost-free) and perturbatively renormalizable. Moreover, we can always find a simple extension...

Topics: General Relativity and Quantum Cosmology, High Energy Physics - Theory, Mathematics, High Energy...

Source: http://arxiv.org/abs/1503.00261

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Sep 23, 2013
09/13

by
Francesco Caravelli; Leonardo Modesto

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In this paper we construct four Kerr-like spacetimes starting from the loop black hole Schwarzschild solutions (LBH) and applying the Newman-Janis transformation. In previous papers the Schwarzschild LBH was obtained replacing the Ashtekar connection with holonomies on a particular graph in a minisuperspace approximation which describes the black hole interior. Starting from this solution, we use a Newman-Janis transformation and we specialize to two different and natural complexifications...

Source: http://arxiv.org/abs/1006.0232v1

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Sep 17, 2013
09/13

by
Leonardo Modesto; Piero Nicolini

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In this paper, we calculate in a transparent way the spectral dimension of a quantum spacetime, considering a diffusion process propagating on a fluctuating manifold. To describe the erratic path of the diffusion, we implement a minimal length by averaging the graininess of the quantum manifold in the flat space case. As a result we obtain that, for large diffusion times, the quantum spacetime behaves like a smooth differential manifold of discrete dimension. On the other hand, for smaller...

Source: http://arxiv.org/abs/0912.0220v3

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Sep 18, 2013
09/13

by
Leonardo Modesto; Carlo Rovelli

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We devise a technique for defining and computing n-point functions in the context of a background-independent gravitational quantum field theory. We construct a tentative implementation of this technique in a perturbatively-finite loop/spinfoam model.

Source: http://arxiv.org/abs/gr-qc/0502036v1

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Jul 19, 2013
07/13

by
Leonardo Modesto; Piero Nicolini

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In this paper we complete the program of the noncomutative geometry inspired black holes, providing the richest possible solution, endowed with mass, charge and angular momentum. After providing a prescription for employing the Newman-Janis algorithm in the case of nonvanishing stress tensors, we find regular axisymmetric charged black holes in the presence of a minimal length. We study also the new thermodynamics and we determine the corresponding higher-dimensional solutions. As a conclusion...

Source: http://arxiv.org/abs/1005.5605v3

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Sep 22, 2013
09/13

by
Cosimo Bambi; Leonardo Modesto

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The formation of spacetime singularities is a quite common phenomenon in General Relativity and it is regulated by specific theorems. It is widely believed that spacetime singularities do not exist in Nature, but that they represent a limitation of the classical theory. While we do not yet have any solid theory of quantum gravity, toy models of black hole solutions without singularities have been proposed. So far, there are only non-rotating regular black holes in the literature. These metrics...

Source: http://arxiv.org/abs/1302.6075v2

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Sep 22, 2013
09/13

by
Francesco Caravelli; Leonardo Modesto

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Using the Wald's relation between the Noether charge of diffeomorphisms and the entropy for a generic spacetime possessing a bifurcation surface, we introduce a method to obtain a family of higher order derivatives effective actions from the entropy of black holes. Our point of view is to consider fundamental the black hole entropy and the action an emerged object. We then specialize to a particular class of effective theories: the f(R) theories. We apply the idea, using a simple mind ansatz,...

Source: http://arxiv.org/abs/1001.4364v3

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Jun 28, 2018
06/18

by
Leonardo Modesto; Ilya L. Shapiro

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We suggest and briefly review a new sort of superrenormalizable models of higher derivative quantum gravity. The higher derivative terms in the action can be introduced in such a way that all the unphysical massive states have complex poles. According to the literature on Lee-Wick quantization, in this case the theory can be formulated as unitary, since all massive ghosts-like degrees of freedom are unstable.

Topics: General Relativity and Quantum Cosmology, High Energy Physics - Theory

Source: http://arxiv.org/abs/1512.07600

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Sep 21, 2013
09/13

by
Leonardo Modesto; Isabeau Prémont-Schwarz

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In this paper we have recalled the semiclassical metric obtained from a classical analysis of the loop quantum black hole (LQBH). We show that the regular Reissner-Nordstrom-like metric is self-dual in the sense of T-duality: the form of the metric obtained in Loop quantum Gravity (LQG) is invariant under the exchange "r a0/r" where "a0" is proportional to the minimum area in LQG and "r" is the standard Schwarzschild radial coordinate at asymptotic infinity. Of...

Source: http://arxiv.org/abs/0905.3170v2

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Sep 19, 2013
09/13

by
Leonardo Modesto; Isabeau Prémont-Schwarz

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In this paper we have recalled the semiclassical metric obtained from a classical analysis of the loop quantum black hole (LQBH). We show that the regular Reissner-Nordstr\"om-like metric is self-dual in the sense of T-duality: the form of the metric is invariant under the exchange r -> a0/r where a0 is proportional to the minimum area in LQG. Of particular interest, the symmetry imposes that if an observer at infinity sees a black hole of mass m an observer in the other asymptotic...

Source: http://arxiv.org/abs/0909.5421v2

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Jun 29, 2018
06/18

by
Cosimo Bambi; Daniele Malafarina; Leonardo Modesto

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In a previous paper, we studied the interior solution of a collapsing body in a non-local theory of gravity super-renormalizable at the quantum level. We found that the classical singularity is replaced by a bounce, after which the body starts expanding. A black hole, strictly speaking, never forms. The gravitational collapse does not create an event horizon but only an apparent one for a finite time. In this paper, we solve the equations of motion assuming that the exterior solution is static....

Topics: High Energy Physics - Theory, Astrophysics, High Energy Astrophysical Phenomena, General Relativity...

Source: http://arxiv.org/abs/1603.09592

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Sep 23, 2013
09/13

by
Cosimo Bambi; Francesco Caravelli; Leonardo Modesto

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Recently, two of us have argued that non-Kerr black holes in gravity theories different from General Relativity may have a topologically non-trivial event horizon. More precisely, the spatial topology of the horizon of non-rotating and slow-rotating objects would be a 2-sphere, like in Kerr space-time, while it would change above a critical value of the spin parameter. When the topology of the horizon changes, the black hole central singularity shows up. The accretion process from a thin disk...

Source: http://arxiv.org/abs/1110.2768v2

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Jun 30, 2018
06/18

by
Cosimo Bambi; Zheng Cao; Leonardo Modesto

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Weyl conformal symmetry can solve the problem the spacetime singularities present in Einstein's gravity. In a recent paper, two of us have found a singularity-free rotating black hole solution in conformal gravity. In addition to the mass $M$ and the spin angular momentum $J$ of the black hole, the new solution has a new parameter, $L$, which here we consider to be proportional to the black hole mass. Since the solution is conformally equivalent to the Kerr metric, photon trajectories are...

Topics: High Energy Astrophysical Phenomena, Astrophysics, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1701.00226

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Sep 23, 2013
09/13

by
Stephon Alexander; Antonino Marciano; Leonardo Modesto

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In this paper we consider the relation between the super-renormalizable theories of quantum gravity (SRQG) studied in [arXiv:1110.5249v2, arXiv:1202.0008] and an underlying non-commutativity of spacetime. For one particular super-renormalizable theory we show that at linear level (quadratic in the Lagrangian) the propagator of the theory is the same we obtain starting from a theory of gravity endowed with {\theta}-Poincar\'e quantum groups of symmetry. Such a theory is over the so called...

Source: http://arxiv.org/abs/1202.1824v1

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Jul 20, 2013
07/13

by
Bernard Carr; Leonardo Modesto; Isabeau Prémont-Schwarz

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The Generalized Uncertainty Principle suggests corrections to the Uncertainty Principle as the energy increases towards the Planck value. It provides a natural transition between the expressions for the Compton wavelength below the Planck mass and the black hole event horizon size above this mass. It also suggests corrections to the the event horizon size as the black hole mass falls towards the Planck value, leading to the concept of a Generalized Event Horizon. Extrapolating below the Planck...

Source: http://arxiv.org/abs/1107.0708v1

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Jun 29, 2018
06/18

by
Cosimo Bambi; Leonardo Modesto; Yixu Wang

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We derive and study an approximate static vacuum solution generated by a point-like source in a higher derivative gravitational theory with a pair of complex conjugate ghosts. The gravitational theory is local and characterized by a high derivative operator compatible with Lee-Wick unitarity. In particular, the tree-level two-point function only shows a pair of complex conjugate poles besides the massless spin two graviton. We show that singularity-free black holes exist when the mass of the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1611.03650

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Jun 30, 2018
06/18

by
Gianluca Calcagni; Leonardo Modesto; Giuseppe Nardelli

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We reinterpret the spectral dimension of spacetimes as the scaling of an effective self-energy transition amplitude in quantum field theory (QFT), when the system is probed at a given resolution. This picture has four main advantages: (a) it dispenses with the usual interpretation (unsatisfactory in covariant approaches) where, instead of a transition amplitude, one has a probability density solving a nonrelativistic diffusion equation in an abstract diffusion time; (b) it solves the problem of...

Topics: High Energy Physics - Theory, Mathematics, Mathematical Physics

Source: http://arxiv.org/abs/1408.0199

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Jun 28, 2018
06/18

by
Yao-Dong Li; Leonardo Modesto; Leslaw Rachwal

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We give here a list of exact classical solutions of a large class of weakly nonlocal theories of gravity, which are unitary and super-renormalizable (or finite) at quantum level. It is explicitly shown that flat and Ricci-flat spacetimes as well as maximally symmetric manifolds are exact solutions of the equation of motion. Therefore, well-known physical spacetimes like Schwarzschild, Kerr, (Anti-) de Sitter serve as solutions for standard matter content. In dimension higher than four we can...

Topics: High Energy Astrophysical Phenomena, Mathematical Physics, General Relativity and Quantum...

Source: http://arxiv.org/abs/1506.08619

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Sep 23, 2013
09/13

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Eric Brown; Robert Mann; Leonardo Modesto

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We study the stability properties of the Cauchy horizon for two different self-dual black hole solutions obtained in a model inspired by Loop Quantum Gravity. The self-dual spacetimes depend on a free dimensionless parameter called a polymeric parameter P. For the first metric the Cauchy horizon is stable for supermassive black holes only if this parameter is sufficiently small. For small black holes, however the stability is easily implemented. The second metric analyzed is not only self-dual...

Source: http://arxiv.org/abs/1006.4164v1

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Jun 28, 2018
06/18

by
Leonardo Modesto; Marco Piva; Leslaw Rachwal

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We explicitly compute the one-loop exact beta function for a nonlocal extension of the standard gauge theory, in particular Yang-Mills and QED. The theory, made of a weakly nonlocal kinetic term and a local potential of the gauge field, is unitary (ghost-free) and perturbatively super-renormalizable. Moreover, in the action we can always choose the potential (consisting of one "killer operator") to make zero the beta function of running gauge coupling constant. The outcome is "a...

Topics: High Energy Physics - Phenomenology, Mathematical Physics, Mathematics, High Energy Physics - Theory

Source: http://arxiv.org/abs/1506.06227